The Division of Neurobiology and Behavior consists of seven independent laboratories: Mammalian neurophysiology, invertebrate neurobiology, neuropsychology, neurochemistry, biophysics, developmental neurobiology and morphology. The research of the Division is directed toward cellular analyses of behavior in selected vertebrates and in Aplysia. Because the brains of higher mammals contain trillions of nerve cells and the simplest behaviors involve actions of diverse cells with complex interconnections, our approach has been to reduce experimental preparations to manageable proportions. In mammals, complexity has been simplified by selecting particular brain systems for study. Thus, voluntary movements that depend on sensory clues being transformed into motor movement in just a few synaptic relays. In Aplysia, even complex behavior is mediated by only a small number of neurons. Because many of these cells can be identified individually by electrophysiological biochemical and morphological techniques, it is possible to correlate behavior and learning with neural function.